Color Enhancement

[riley540]

What does it mean when it says a poster has had the colors "enhanced"? Does it mean it's all just been painted over? How else would you enhance faded colors?

Thanks!

[BwanaDik]

Either the poster got bleached; either painted over.

Some professionals will bleach paper to make it brighter and remove impurities, bleaching is dangerous business as acid is added in the paper, so it requires at least two alkaline bath to neutralise the acidity; at the end, it does enhance colors - "During the linen backing process, the poster will be cleansed of impurities using a gentle aqueous process. If so desired the paper can also be bleached to treat any mildew growth or acid discoloration. The bleach used by paper conservators is designed to only affect the paper and never the printing ink, though the brightening of the paper can make the ink appear brighter."

[riley540]

Thanks for the info! Did you take that quote from somewhere specific?

I appreciate it!

[BwanaDik]

From there - https://www.ivpda.com/content/396/Linen-Backing-Posters

Note they use the general term "bleach/bleaching", as to know the exact composition of their bleaching and ratio, you need to consult Google :)

But this paper is a good start - https://www.conservation-wiki.com/wiki/BPG_Bleaching
Most common bleaching are potassium hypochlorite (bleach), calcium hypochlorite or sodium hypochlorite, because there are easily soluble in water allowing aqueous treatment by immersion.   This said, bleaching is coarse process; it can be difficult to control as they are effective stain remover.  It is a tedious process as it requires full washing, anti-chlor bath and/or alkaline bathes to buffer the chlore/acid.  Some will do partial bleaching (that is applying the bleach at the bad places) but it is preferable to do a full immersion bath with low ratio to have a better controlled and uniform bleaching process.    Some will avoid bleaching for the reasons mentioned above and use other methods (also mentioned in the report)